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wards and inwards, while the angles are directed upwards,
downwards and outwards. The anterior surface has a furrow,
called the hilum, which passes horizontally a little below the
upper border and vertically near the inner border. At the
union of these two parts of the fissure the capsular vein emerges from the organ.
The area above and internal to the fissure is depressed and forms about one-third
of the anterior surface. The inner part of this area lies behind the inferior vena
cava, and the upper part is in direct contact with the liver. The outer and larger





B




Fig. 310. ANTERIOR SURFACE CF

THi: SUPRARENAL CAPSULES,
MODIFIED FROM ROLLESTON.

(J. S.)

A, right capsule, s, c, i, its supe-
rior, external and inferior angles ;

a, area in direct contact with liver ;

b, area behind inferior vena cava ;

c, area, below and external to the
fissure, covered by the peritoneum
and the liver except near the inferior
angle where it comes in contact with
the duodenum ; d, fissure on ante-
rior surface ; /, vein.

B, left capsule, s, its superior
angle ; d, fissure on anterior sin
face ; /, vein ; L. If, left renal vein :
L.S, left spermatic vein.

portion of the anterior surface is covered by the peritoneum, which separates it
from the liver, except a small area near the inferior angle, which sometimes lies
against the duodenum. The posterior surface also has a depression dividing it
into two parts, one of these, the upper and larger, lies against the diaphragm, and
is bounded below by an elevation projecting into the groove between that muscle
and the kidney ; the lower and smaller area is in contact with the kidney.

The left suprarenal capsule is slightly larger than the right. It does not
project so much above its corresponding kidney, but is prolonged downwards along
the upper half of its inner border. Looked at from the front, its outline is
crescentic, the concavity of the crescent being directed downwards and outwards
towards the kidney. The anterior surface lies in contact with the upper end of the
renal surface of the spleen and the stomach near its cardiac orifice, while its lower
half is crossed by the pancreas and the splenic vessels. It has a groove passing



THE SUPRARENAL CAPSULES.



303



downwards and forwards, at the lower end of which the suprarenal vein emerges.
The posterior surface is divided into two parts by a prominent vertical ridge, the

Fig. 311. SECTION OF THE SUPRARENAL BODY. (Allen Thomson.)

A vertical section of the suprarenal body of a foetus, twice the natural size, showing
the lower notch by which it rests on the summit of the kidney (), and the anterior
notch by which the suprarenal vein (v] issues, together with the distinction between
the medullary and cortical substance.

area mesial to the ridge looking inwards and backwards and resting
upon the left eras of the diaphragm and the lateral area outwards as
well as backwards against the kidney. *

The suprarenal capsules measure from l in. to 2| in. (30 mm.
to 60 mm.) from above downwards and about lj in. (30 mm.) from
side to side ; their thickness is from |th in. to in. (4 mm. to 6 mm.),
the left being usually thicker than the right. The weight of each in the adult
is about 1 drachm (4 grammes), the left being slightly the heavier. They are
nearly as large at birth as in adult life.

Structure. Besides a covering of areolar tissue mixed frequently with much






Fig* 312. VERTICAL SECTION OP SUPRARENAL BODY: HUMAN. MAGNIFIED. (Eberth.)
f 1, cortical substance ; 2, medullary substance : a, capsule ; b, zona glomerulosa ; c, zona fasciculata ;
d, zona reticularis ; e, groups of medullary cells ; /, section of a large vein.

Fig. 313. SECTION OP THE CORTEX OP THE DOG'S SUPRARENAL. (Bohm and v. Davidoff.)
o, fibrous covering ; b, zona glomerulosa ; c, zona fasciculata ; jd. zona reticularis.

1 The above description is based largely upon the account of these organs given by H. D. Kolleston
(Journal of Anatomy and Physiology, vol. xxyi,).



304.



THE DUCTLESS GLANDS.



fat, the suprarenal capsules have a thin fibrous investment. On the exterior their colour
is yellowish or brownish-yellow. When cut into (fig. 311) they are seen to consist
of two substances : one, external or cortical, of a deep yellow colour, firm and
striated, and forming the principal mass of the organ ; the other, internal or
medullary, in the adult of a dark brownish-black hue, and so soft and pulpy that
seme anatomists have erroneously described a cavity within it.

The fibrous coat (figs. 312, 313, ), which is distinguishable into an outer
looser and an inner firmer part, is so intimately connected with the deeper parts
that it cannot be removed without lacerating the subjacent structure. Its deeper
layers contain plain muscular cells, at least in some animals : it is continuous with
the septa which enter into the formation of the substance of the organ.

The cortical part of the suprarenal body, examined in a section with a low magni-
fying power (fig. 312, 1 ; fig. 313), is seen to consist of a fibrous stroma, in which are
embedded column-like, intercommunicating groups of cells (c). The groups measure
on an average T ^th inch ('036 mm.) in diameter, and are arranged vertically to the
surface of the organ. In the deepest part of the cortex, however, the colour is darker,
and the columnar arrangement is lost, the stroma being more equally distributed (d) :
and immediately beneath the fibrous coat there is another narrow zone in which the
stroma encloses what in section look like rounded or oval spaces occupied by groups
of cells, which are really the outer ends of the columnar groups above mentioned (b).
These inner and outer layers have been named respectively zona reticularis and sot) a
glomerulosa, and the term zona fasciculata is applied to the main part (c) ; but the
transition from one of these parts to another is in man not sudden nor indicated by
any sharp line o.l' demarcation.

The cells which form the groups and columns of the cortical substance are





Fig. 314. CELLS AND CELL-GROUPS FROM THE OUTERMOST LAYER OF THE CORTICAL SUBSTANCE OF THE

SUPRARENAL BODY. HIGHLY MAGNIFIED. (Ebei'th. )
Fig. 315. A SMALL PORTION OF THE MEDULLARY TART OF THE SUPRARENAL CAPSULE OF THE OX

(Eberth.) HIGHLY MAGNIFIED.

polyhedral in form (fig. 314) : their protoplasm is finely reticular, and not
unirequently contains yellowish oil globules. The cells vary from -0125 mm. to
02 mm. in diameter.

In some animals (horse, dog, cat), the spaces of the zona glomerulosa are occupied
by regularly arranged long columnar cells, set around a sort of lumen, and looking
not unlike part of a glandular tube (fig. 313, J). In man, however, most of the cells
of this part are polyhedral, like those of the other zones.

The medullary part (fig. 312, 2) of the suprarenal capsule is marked off from
the cortical part by a layer of loose connective tissue. In the thinner parts of the
adult organ there is no medullary part, and the layer of connective tissue referred
to is found separating the deep surfaces of two opposed portions of the cortical part ;
but in the young state the distinction of cortical and medullary portions probably



THE SUPRARENAL CAPSULES. 305

extends throughout the whole gland. The medullary part is pervaded by large
venous capillaries, which receive the whole of the blood which has passed through
the organ. These venous capillaries are supported by the fibrous -stroma, which
also contains, especially in man, a number of bundles of plain muscular cells
disposed parallel to the course of the larger veins, and forming a complete invest-
ment to the issuing suprarenal vein (v. Brunn). The general arrangement of the
stroma is reticular ; in its meshes are enclosed groups of cells (fig. 315), which diifer
from those of the cortex in being more irregular in form, larger in size, of a clearer
aspect, and destitute of oil-globules. They are frequently highly vacuolated.
Moreover they become stained of a deep brown colour by solutions of bichromate
of potash, whereas the cortical cells are but slightly tinged by that re-agent.

In some animals the medullary cells contain a large amount of reddish-brown pigment,
which marks the medulla off sharply from the cortex, but this is not generally the case in the
human subject, the deep colour of the medulla being chiefly due to the blood within its
numerous vessels.

Varieties. One or both capsules may be absent, although this is very rarely the case.
Accessory suprarenal capsules are occasionally met with varying in size from a pin's
head to that of a large pea. The smaller ones have no medullary substance, but the large ones
possess a medulla (Rolleston). The accessory capsules are generally found near or upon the
capsule itself and united to it by connective tissue. Sometimes they are partially embedded
in the kidney or liver, and Marchant has found them in the broad ligament of the uterus,
and Schmorl on the spermatic vessels near the inguinal canal.

Arteries and veins. The suprarenal bodies receive arteries from three
sources, viz., from the aorta, the phrenic and the renal arteries. All these arteries
break up into small branches before entering the capsule. The veins, which pass out
from the centre, are usually united into one for each organ. The right vein enters
the inferior vena cava immediately, while the left, after a longer course, terminates
in the left renal vein.

The small arteries, entering from the surface, run in the septa parallel to the
columns, frequently anastomosing together, and surrounding each group of cells
with a fine capillary network. From these capillaries the blood is continued
into the medulla, where it is collected into the large venous capillaries already
mentioned. The chief efferent vein emerges at the hilum. According to
Pfaundler, none of the vessels of the suprarenals have any coat other than the
endothelium.

Lymphatics run in the trabeculse of the cortical substance and are connected
with cleft-like spaces between the trabeculas and the cell-columns, and even with fine
clefts between the cells within the columns (Klein). They communicate with
efferent valved lymphatics both in the fibrous coat and in the medulla, where they
are very numerous, forming an especially close plexus around the central vein.

Nerves. The nerves, which are exceedingly numerous, are derived from the
solar plexus of the sympathetic and from the renal plexuses. According to
Bergmann some filaments come from the phrenic and pneumo-gastric nerves. They
are made up mainly of medullated fibres of different sizes, and they have many small
ganglia upon them before entering the organ. The nerves are especially numerous
on the lower half and inner border. They ramify between the cells of the cortex,
where they are especially abundant in the zona glomerulosa. In the medulla they
are connected with numerous small ganglion-cells, and are distributed to the blood-
vessels and amongst the glandular cells.

Function. Removal of the suprarenal bodies in animals is speedily followed by symptoms
of extreme muscular prostration and, within a very few days, by death (Brown-Sequard,
1856). Disease of the organs is usually accompanied by the appearance of bronzed patches on
various parts of the skin and mucous membranes (Addison, 1855), and the symptoms in ad-

V OL. III., VI. 4. X



306 THE DUCTLESS GLANDS.

vanced disease are similar to those resulting from removal. The watery extract of the medulla
of the capsules contains a (non-proteid) substance which produces when injected even in
minute quantities into the blood-vessels of an animal, a great augmentation of the contraction
of the muscular tissue of the heart and arteries, and prolongs the contractions of the skeletal
muscles (Oliver and Schafer, 1894).

RECENT LITERATURE OF THE SUPRARENALS.

Alexander, Carl, Untersuchungcn ueber die Nebcnnieren und ihre Beziehungen zum Ncrven-
system, Beitrage zur pathologischen Anatomie und zur allgemeinen Pathologic, Ed. xiv., 1891.

Arren, L., Essai sur les capsules surrenales, These, Paris, 1894.

Biasing-, Karl, Ueber die Nebennieren und den Sympathicus bei Anenccphalen, Bonn, C.
Georgi, 1886.

Brandt, Alexander, Ueber den Zusammenhang der Glandula suprarenalis mit dem Parovarium
resp. der Epididymis bei Huhnern, Biolog. Centralbl., Bd. ix., 1889.

Canalis, P., Contribution a Vetude du developpement et de la pathologic des capsules surrenales,
Internationale Monatsschrift fur Anatomie, Bd. iv.

Carlier, E. W., Note on the structure of the suprarenal body, Anat. Anzeiger, Jg. viii., 1893.

Chiari, H. , Zur Kenntniss der acccssorischen Nebennieren des Menschcn, Ztschr. f. Heilk.,
Prague, 1884.

Dogiel, A. S., Die Nervenendigungen in den Nebennieren der Sdugetiere, Arch. f. Anat. u.
Physiol., Anat. Abth., 1S94.

Dostoiewsky, G., Ein Beitrag zur mikrosJcopischen Anatomie der Nebennieren bei Sdugethicren,
Archiv fiir mikroskopische Anatomie, Bd. xxvii.

Fusari, Borneo, Sulla terminazione delle fibre nervose nelle capsule surrenali dei mammiferi,
Atti della E. Accad. delle Scien. di Torino, vol. xxvi. 1890-91 ; De la terminaison des fibres nerveuxes
dans les capsules surrenales des mammiferes, Archives italiennes de biologic, t. xvi., 1891.

Gruarneri, J., et Magini, J., Studie sulla fina struttura delle capsule suprarenali, Atti della R.
Accademia dei Lincei, 1888 ; Etudes sur la fine structure des capsules surrenales, Archives italiennes
de biologic, tome x., 1888.

Janosik, J., Bemerlcungen iiber die EntwicTcelung der Nebenniere, Arch. f. mikr. Anat., 1883.

Liebmann, Arthur, Ueber die Nebennieren und den Sympathicus bei Hemiccphalen, Bonn,
1886.

Mag-nus, Rich., Ueber das anatomische Verhalten der Nebennieren, der Thyreoidea und Thymus
und des Sympathicus bei Hemicepkalen, Konigsberg, 1889.

Manasse, Paul, Uber die eziehungen der Nebennieren zu den Venen und dem venosem Kreislauf,
Arch. f. path. Anat., Bd. cxxxv., 1894.

Marchand, Beitrdge zur Kenntniss der normalen und pathologischen Anatomic der Glandula,
carotica und der Nebennieren, Internat. Beitrage zur \vissenschaftl. Medicin, Virchow Festschrift,
Bd. i., 1891 ; Ueber accessorische Nebennieren im Ligamentum latum, Virch. Arch. f. path. Anat.,
Bd. xcii.

Martinotti, C., Contribute olio studio delle capsule surrenali, Ann. di freniatr., 1891-92, v. iii. ;
and Giorn. d. r. accad. d. med. d. Torino, 1892.

Mattel, Sulle fibre muscolari liscie delle capsule soprarenali allo stato normale e patoloyico,
Giornale della R. Accademia di Medicina di Torino, anno xlix., 1887.

Michael, Zum Vorkommen accessorischen Nebennieren, Deutsches Archiv fur klinische Chirurgie,
Bd. xliii., 1888.

Miuot, C. S., Morphclogy of the suprarenal capsules, Proc. Amer. Assoc. for the Adv. of Science,
vol. xxxiv.

Oliver, G-. and Schafer, E. A., On the physiological action of extract of the suprarenal
capsules, Journal of Physiology, 1894 and 1895.

Pfaimdler, Zur Anat. der Nebenniere, Sitzungsb. der Wiener Akad., 1892.

Pilliet, A. H., Capsule surrenale sous la capsule fibreuse du rein droit, Bull, de la soc. anat. de
Paris, annee 68.

Rabl, Hans, Die Entwiclcelung und Struktur der Nebcnnieren bei den Vogeln, Archiv f.
mikroskop. Anatomie, Bd. xxxviii., 1891.

Rolleston, H. D., Note on the anatomy of the suprarenal bodies, The Journ. of Anat. and
Physiol., vol. xxvi., 1892 ; The Gulstonian Lectures on the suprarenal bodies, Brit. Med. Jour.,
1895, vol. i.

Solger, R., Anatom. Einleitung: Harnapparat, Nebenniere, Klin. Hdb. d. Harn- und Sexualorg,
von. W. Ziilzer, Leipzig, 1894.

Stilling 1 , H., Zur Anatomie der Nebennieren, Virchow's Archiv f. path. Anat., Bd. cix., 1887.

"Weldon, "W. F. R., On the suprarenal bodies of vertebrata, Quart. Jour. Micr. Science, 1885.

Zander, R., Ueber funktionelle und genetische Beziehunc/en der Nebennieren zu andercn Organen,
speziell zum Grosshirn, Beitr. z. pathol. Anat. v. E. Ziegler, Bd. vii., 1890.



THE THYMUS GLAND.



307



THE THYMUS GLA.ND.



The thyiuus gland or body is a temporary organ which reaches its greatest size
at about the end of the second year of life, after which period it ceases to grow,
and is gradually reduced to a mere vestige. Its function is not fully understood,
although it is probable that it is in some way connected with the elaboration of the
blood in infancy. When examined in its mature state in an infant under two years
of age, it appears as a narrow elongated glandular-looking body, situated partly in
the thorax, and partly in the lower region of the neck (fig. 316) : below, it lies in




Fig. 316. THE THYMUS IN A CHILD OF six MONTHS. (Sappey.)

A. Situation, form and relations of the gland. 1, right lobe ; 2, left lobe ; 3, median furrow ; 4,
lung, somewhat everted ; 5, internal mammary vein ; 6, thyroid body ; 7, inferior, 8, middle thyroid veins ;
9, common carotid artery ; 10, internal jugular vein ; 11, pneumo-gastric nerve. B. Right lobe of the
thymus after removal of its envelope ; 1, its apex ; 2, its base ; 3, thin outer border ; 4, thick inner
border. C. The gland unravelled, showing the lobules, 3, grouped around a central cord ; 4, the central
cord or strand of connective tissue, connecting the lobules.

the superior and anterior mediastinal spaces close behind the sternum as far down
as the fourth rib-cartilage, and in front of the great vessels and pericardium ; above,
it extends upwards upon the trachea in the neck as high as the lower border of the
thyroid body, being covered by the sterno-hyoid and sterno-thyroid muscles. Its
colour is greyish, with a pinkish tinge ; its consistence soft and pulpy, and its
surface appears distinctly lobulated. It consists of two lateral lobes, which touch
each other along the middle line, and are of a nearly symmetrical long pyramidal
form, though generally unequal in size, sometimes the left, and at other times the
right lobe being the larger of the two. An intermediate lobe often exists between the
two lateral ones, and occasionally the whole body forms a single mass.



308



THE DUCTLESS GLANDS.



Externally the gland is in contact with the pleura, near the internal mammary
artery, and higher up (in the neck), with the sheath of the carotid artery. The
dimensions of the thymus vary according to its stage of development. At birth it,
measures rather more than two inches (60 mm.) in length, an inch and a half
(37 mm.) in width at its lower part, and about one quarter or one third of an inch
(6 8 mm.) in thickness. Its weight at this period was found by Testut, on an
average of twenty cases, to be 5 grammes.

At puberty the thymus is generally reduced to a mere vestige which has entirely lost its
original structure, and consists of brownish tissue occupying part of the superior mediastinum.
Occasionally it is still found in good condition at the twentieth year ; but generally only
traces of it remain at that time, and these are rarely discoverable beyond the twenty-fifth or
thirtieth year.

Structure. The lateral lobes of the thymus gland are each invested by a thin
capsule of areolar tissue, which sends partitions into the gland between the lobules :
on its outer surface the capsule is covered by a layer of flattened cells. Each lobe




Fig. 317. FROM A SECTION OF THE THYMUS or A CHILD. (E. A. S.)

c, cortex of a lobule partly separated into nodules by the trabeculae, tr. ; b, b, blood-vessels and
c, c, connective tissue corpuscles in the medulla.

consists of numerous polyhedral lobules, connected by a more delicate intervening
areolar tissue. These primary lobules are made up of a number of small nodules or
follicles (fig. 317), one to two millimeters in diameter. Each follicle is composed
of a central part or medulla, and an external larger part or cortex. The cortex is
in many respects similar in structure to an ordinary lymphoid follicle, such as
those of the tonsils or of Peyer's patches in the intestine : consisting, like these, of
retiform tissue composed of a fine reticulum of fibres, the meshes being filled with
lymphoid cells (thymus corpuscles}. At the surface of the follicle the retiform tissue
is somewhat closer, so as to form a species of capsule for it. In some animals these
capsules completely enclose the follicles, but in others, including man, several follicles
may be united towards the centre of the lobule (see fig. 817), which is then com-
monly of softer consistence than the other parts, and apt to break down if not
perfectly fresh, so as to give the deceptive appearance of a central cavity.

In the medulla, the retiform tissue is coarser and the lymphoid cells fewer ; but
it contains here and there nests of cells which have a concentric structure, and are
known as the concentric corpuscles of Hassall. They vary in size from 0'025 mm. to
three times that diameter, or more ; the larger ones (compound corpuscles) often
contain smaller ones in their interior (fig. 318).




THE THYMUS GLAND. 309

Each nest is composed of an envelope of keratinized epithelium-like cells enclosing
a central mass, formed of one or more granular cells. Cells like those_in_the centre
of the nest are also found, unenclosed, in the retiform tissue of the follicle, and
occasionally attain a large size (giant-cells). The concentric corpuscles are vestiges of
the original epithelial tube which is found in the developing thymus (see Vol. I., Pt. 1,

Fig. 318. PART OF THE MEDULLA OF A THYMUS GLAND SHOWING THE RETI-

CULUM, THE LYMPHOID CELLS OR THYMUS CORPUSCLES AND TWO CONCEN-
TRIC CORPUSCLES. (Cadiat. )

p. 111). According to some authorities the thymus corpuscles
are also of epithelial (i.e., hypoblastic) origin, and are not derived
as has usually been believed, from the surrounding mesoblastic
tissue. Small portions of thymus tissue are constantly found,
according to Kohn, in association with the thyroid and para-
thyroids. Schaffer describes in the thymus nucleated red blood
corpuscles like those met with in bone-marrow.

The retrogressive development of the gland is accompanied by an increase in the
interstitial connective tissue, which also invades the follicles. In this tissue plasma-
cells become accumulated, and then appear to be eventually transformed into fat-
cells, the normal structure of the thymus becoming gradually obliterated. It has
been shown, however, by Waldeyer, that even in advanced age not only can the
original shape of the thymus be distinctly made out, but that in addition there are
constantly to be found traces of its original structure in the form of small masses
of thymus corpuscles and even of concentric corpuscles.

Vessels and Nerves. The arteries of the thymus are derived from various
sources, viz., from the internal mammary, the inferior and superior thyroid, the
subclavian and carotid arteries. Their branches penetrate to the follicles, where
they form a plexus which surrounds the cortex and from which capillaries converge
towards the medulla. In some animals these vessels loop back towards the cortex,
but in others they open into an inner vascular circle which lies just within the
boundary of the medulla. The veins, for the most part, open into the left
innominate vein.

The lymphatics are large. According to the observations of His on the calf, the
larger blood-vessels passing to the centre are each accompanied by two or more
lymphatic trunks. These arise from an interlobular plexus, which again is in
connection with vessels which surround and enclose the individual follicles without
penetrating them (as in those of the intestine).

The nerves are very minute. Haller thought that they were partly derived from
the phrenic nerves, but according to Cooper, no filaments from these nerves go into
the gland, although they reach the investing capsule, as does also a branch from the
descendens nypoglossi. Small filaments, derived from the pneumo-gastric and sympa-
thetic nerves, descend, on the thyroid body, to the upper part of the thymus.
Sympathetic nerves also reach the gland along its various arteries.



RECENT LITERATURE OP THE THYMUS GLAND.

Beard, J. , The development and probable function of the thymus, Anat. Anzeiger, Bd. ix., 1894.

Capobianco, Contrib. ft la morphol. du thymus, Arch. ital. de biol., xvii., 1892.

Flemming-. "W., Die ZellvermehruHg in d. Lymphdriisen u. verwand. Onjanen, <L-c., Arch. f.
mikr. Anat., xxiv., 1885.

Qulland, The development of adipose tissue with especial, reference to the tonsil and thymus,
Labor. Reports of the R. Coll. of Physicians of Edinburgh, vol. iii. , 1891.

Moiiguidl, C., Sulla glandola timo, Parma, 1885.



310 THE DUCTLESS GLANDS.

Schaffer, Josef, Uebcr das Vorkommen eosinopkiler Zdlen in der menschlifJien Thymus,



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